Why mail should be routed through the alpha.Tempest2.com domain is beyond me anyway. All I know, is that mail is no longer working, and when you send something to their e-mail addresses, it is bounced back with the above error.

Now, as soon as I realised this, I did the normal thing, changed hostname back to what it was - but this doesnt seem to have done anything (and anyway, the routed domain name is Tempest2 and not tempest2 - which was what i changed it to [lower case t]).

So I go on our little page for mrtg which calls upon server hostnames, and I find that it is now no longer working (for some bizarre reason).. here's the error for that: